Conversion of Sweet Whey to Bioethanol: A Bioremediation Alternative for Dairy Industry

In many countries, whey from the dairy industry is an abundant waste that generates an important environmental impact. Alternative processes to use the whey and minimize the environmental impact are needed. This work considered six formulations with different ammonium sulfate and L-phenylalanine (L-Phe) concentrations to produce bioethanol in sweet whey fermentation by Kluyveromyces marxianus. The results showed a maximum bioethanol concentration equal to 25.13 ± 0.37 g L−1 (p < 0.05) for formulation F6, with 1 g L−1 of L-Phe and 1.350 g L−1 of ammonium sulfate (96 h). For these conditions, the chemical oxygen demand removal percentage (CODR%) was 67%. The maximum CODR% obtained was 97.5% for formulation F3 (1 g L−1 of L-Phe) at 96 h; however, a significant decrease in bioethanol concentration (14.33 ± 2.58 g L−1) was observed. On the other hand, for formulation, F3, at 48 h of fermentation time, a bioethanol concentration of 23.71 ± 1.26 g L−1 was observed, with 76.5% CODR%. Based on these results, we suggest that the best conditions to obtain a significant bioethanol concentration and CODR% value are those used on the configuration F3 at 48 h.